Wireless Communications Networks
Embodiments herein are applicable to both cellular and non-cellular wireless communications networks.
In a typical cellular wireless communications network, wireless communication devices, also known as mobile stations and/or User Equipments (UEs), communicate via a Radio Access Network (RAN) to one or more core networks. The RAN covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a Radio Base Station (RBS), which in some networks may also be called, for example, a “NodeB” or “eNodeB”. A cell is a geographical area where radio coverage is provided by the radio base station at a base station site or an antenna site in case the antenna and the radio base station are not collocated. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. Another identity identifying the cell uniquely in the whole mobile network is also broadcasted in the cell. One base station may have one or more cells. A cell may be downlink and/or uplink cell. The base stations communicate over the air interface operating on radio frequencies with the user equipments within range of the base stations.
A Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the second generation (2G) Global System for Mobile Communications (GSM). The UMTS Terrestrial Radio Access Network (UTRAN) is essentially a RAN using Wideband Code Division Multiple Access (WCDMA) and/or High Speed Packet Access (HSPA) for user equipments. In a forum known as the Third Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for third generation networks and UTRAN specifically, and investigate enhanced data rate and radio capacity. In some versions of the RAN as e.g. in UMTS, several base stations may be connected, e.g., by landlines or microwave, to a controller node, such as a Radio Network Controller (RNC) or a Base Station Controller (BSC), which supervises and coordinates various activities of the plural base stations connected thereto. The RNCs are typically connected to one or more core networks.
Specifications for the Evolved Packet System (EPS) have been completed within the 3rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases. The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a variant of a 3GPP radio access technology wherein the radio base station nodes are directly connected to the EPC core network rather than to RNCs. In general, in E-UTRAN/LTE the functions of a RNC are distributed between the radio base stations nodes, e.g. eNodeBs in LTE, and the core network. As such, the Radio Access Network (RAN) of an EPS has an essentially “flat” architecture comprising radio base station nodes without reporting to RNCs.
A Wireless Local Area Network (WLAN) is a wireless non-cellular computer network that links two or more devices using a wireless distribution method within a limited area such as a home, school, computer laboratory, or office building. This gives users the ability to move around within a local coverage area and still be connected to the network, and may provide a connection to the wider Internet. Most modern WLANs are based on IEEE 802.11 standards, marketed under the Wi-Fi brand name.
Positioning Techniques
Over the past few years, indoor positioning using wireless communications networks has received considerable attention due to the ever increasing demand on location-awareness in various sectors. So far, most of the efforts have been made to increase the localization accuracy using advanced technologies, for instance statistical sensor fusion attempts to optimally fuse different types of position-related measurements, such as Round-trip-Time-Of-Arrival (RTOA), Received-Signal-Strength (RSS), Angle-Of-Arrival (AOA), speed, and acceleration measured from indoor wireless infrastructures. Such indoor wireless infrastructures may for instance be Wi-Fi networks and Bluetooth Low-Energy (BLE) networks and Inertial Measurement Units (IMU).
Among other types of radio measurements, RSS is more widely used for indoor positioning owing to the fact that no additional hardware is required in the existing wireless communication networks, such as ZigBee networks, Wi-Fi networks, BLE networks, as well as LTE mobile networks.
There exist various RSS based positioning techniques. For one example, RSS fingerprinting is one of the most commonly used positioning techniques. But before such a positioning system may be used to estimate a position, an RSS fingerprint database or a radio map must be constructed beforehand. Each entry in the database is a mapping between a position and a location dependent RSS fingerprint. Statistical modeling is also widely used for RSS based indoor positioning. The resulting probabilistic methods take advantage of the statistical properties of the RSS model parameters.
Recently, another research area, namely proximity based indoor positioning, is becoming more and more popular. This is due to nice features and large market penetration brought about by the resulting low-cost and low-complex positioning system. One way of obtaining proximity information is to compare RSS with a reporting or proximity threshold, denoted as Pth in the sequel. The proximity of a target device, such as a wireless communications device, to a reference network node, such as a base station or BLE beacon, is defined as zero for an RSS value below the threshold value Pth, and defined as 1 for an RSS value above the threshold value Pth. This is also expressed in the equation below.
  Proximity  ⁢          ⁢      =    Δ    ⁢      {                                                      0              ,                                                                          R                ⁢                                                                  ⁢                S                ⁢                                                                  ⁢                S                            ≤                              P                                  t                  ⁢                                                                          ⁢                  h                                                                                                        1              ,                                                                          R                ⁢                                                                  ⁢                S                ⁢                                                                  ⁢                S                            ⁢                                                          >                              P                                  t                  ⁢                                                                          ⁢                  h                                                                        .      
Thus, a proximity measurement obtained in the above way reveals whether or not a target of interest is in the coverage area, which depends on the threshold, of a reference network node. The reference network node serves as a transmitter with preferably low transmit power and transmits broadcast signals and information regularly, or according to a known pattern. The information may contain useful information such as sensor ID, position, network configurations, etc. The reference network nodes may also only transmit a reference signal or identifier, and any other information about the deployment has to be retrieved from some inventory database.
Instead of giving an accurate position estimate with unaffordable cost, the ambition of a proximity based positioning system is to promptly, possibly in real time, identify which zone the target of interest is in, or about to enter, or leave and trigger events or performance reports accordingly. For example, proximity measurements may be subject to event-driven reporting to a network node. This will provide the network node with a time series of reporting events, from which the network node may determine the proximity state of a wireless communications device with respect to transmitters of the RSS-signal. The resulting system will revolutionize mobile applications that are convenient to use in shopping malls, museums, hospitals, hotels, offices, and airports among other sites.
Events Driven Reporting and Measurements
In many wireless communication networks, event driven reporting and measurements are widely used. One example of such event based reporting of measurements is described in “Mobile Station Measurements with Event-Based Reporting”, Gunnar Bark, Joakim Bergström, Walter Muller, September 2002, U.S. Pat. No. 6,445,917 B1. A terminal measures one or more radio-related parameters for one or more cells. The measured parameters are evaluated at the terminal with respect to a predetermined event or condition. Then, the terminal sends a report to the wireless communications network based on the evaluation, e.g., the predetermined event occurs or the condition is satisfied. The wireless communications network may take some action, if appropriate, using the report, e.g., to perform a handover operation. The interaction between the network node and the terminal may be via a Radio Resource Control (RRC) protocol in case the network node is a radio access network node. It can also be an LTE Positioning Protocol (LPP) in case the network node is an Evolved Serving Mobile Location Center (E-SMLC). It may also be via an Access Network Discovery and Selection Function (ANDSF) between a terminal and a network node. It may also be via protocols over the application layer.
Problems with Existing Solutions
Existing positioning methods using RSS measurements may have different problems which remain to be solved.
For example, positioning methods such as fingerprinting require a lot of efforts and have high complexity. This on one hand may increase terminal complexity, which is not desirable. On the other hand, high complexity will further lead to non-scalability from the network side. For example, a lot of computation may be required for the network if there are too many users. Current positioning techniques also require heavy signaling overhead. For example, a lot of data, e.g. RSS measurements, need to be sent to the network.
Furthermore, a badly chosen reporting threshold results in degradation of the positioning performance.